The Midwest Roybal Center for Health Maintenance will have a Statistical Core to provide sound approaches to research design, methodological and statistical problems, and to provide data base design and management assistance to all projects. The Statistical Core will assure that common problems across research projects will share common solutions. Staff will advise pilot PIs on how to maximize the methodological soundness of their projects and will work with Faculty Researchers on each project to assure the highest quality research. The Core will provide overall direction on data analyses to all projects and will provide consultation on design and analyses to pilot project investigators. In particular the Statistical Core staff will keep pace with developments in longitudinal data analyses and communicate those developments to project investigators. The various decisions embodied in the four project proposal reflect our best understanding of what is appropriate at present, but the pace of development in the field is so fast that we expect to make many adjustments over the life of the Center.